Opioid use has increased dramatically in recent years, with rates especially high among women living in poverty. Maternal opioid use combined with poverty renders children highly vulnerable to a host of short- and long-term challenges developing self-regulatory capabilities. In infancy, challenges in self- regulation can be seen in problems in the regulation of attachment behaviors, autonomic nervous system activity, and production of steroid hormones. Sensitive parenting is especially important for such children. Without intervention, many children born to opioid dependent mothers are unlikely to receive sensitive parenting. Early intervention is needed that helps these mothers provide sensitive care despite the challenges of substance use. In this project, we will assess the efficacy of a home visiting program adapted for mothers with opioid dependence who are living in poverty. Mothers on medication assisted treatment for opioid dependence during their third trimester of pregnancy will be randomized to this adapted home visiting program, modified Attachment and Biobehavioral Catch-up (mABC: N=100), or to a control condition of the same duration and frequency (modified Developmental education for Families, or mDEF: N=100). We will assess whether the mABC intervention engages the purported treatment mechanism, maternal sensitivity. Second, we examine whether the intervention has positive effects on infants? regulation of cortisol production, autonomic nervous system activity, and attachment. Third, we examine whether maternal sensitivity mediates intervention effects on infant outcomes. An exploratory aim examines whether the intervention alters maternal neural activity related to the rewarding nature of babies versus drugs. Parental sensitivity will be assessed prenatally, and at infant ages of 1 week, and 3, 6, and 12 months of age, and maternal neural activity will be assessed prenatally and at infant age of 12 months. Infant cortisol will be assessed at 3, 6, and 12 months, autonomic nervous system regulation at 6 and 12 months of age, and attachment at 12 months. The mABC intervention is expected to affect child behavioral and biological outcomes with these effects mediated by maternal sensitivity.